Some types of partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), cochlear implant, or other hearing assistance systems utilize components disposed within the middle ear or inner ear regions. Such components might include an input transducer for receiving sound vibrations or an output stimulator for providing mechanical or electrical output stimuli corresponding to the received sound vibrations.
An example of such a device is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaefer on Mar. 8, 1988. In the '366 patent, a mechanical-to-electrical piezoelectric input transducer is associated with the malleus, transducing mechanical energy into an electrical signal, which is amplified and further processed by an electronics unit. A resulting electrical signal is provided to an electrical-to-mechanical piezoelectric output transducer that generates a mechanical vibration coupled to an element of the ossicular chain or to the oval window or round window for assisting hearing. In the '366 patent, the ossicular chain is interrupted by removal of the incus. Removal of the incus prevents the mechanical vibrations delivered by the piezoelectric output transducer from mechanically feeding back to the piezoelectric input transducer.
Introducing components into the middle or inner ear regions typically involves intricate surgical procedures for positioning or affixing the components for communication or coupling to the desired auditory elements. The proper positioning and affixation for obtaining the best input signal and providing the best output stimuli is a difficult task. The patient is typically under general anesthesia, and is thus unable to provide the implanting physician with any information regarding how well sound is being perceived. Thus, the implanting surgeon faces a difficult task that may yield uneven results in the proper positioning and affixation of components in the middle or inner ear regions in order to obtain proper sound perception.
Other complicating factors are also present. There may be a large variations between patients in the sound perception characteristics of their auditory systems. Moreover, there may be variations between hearing assistance systems, such as in their component characteristics, for example, the characteristics of the input transducer and output stimulator may well vary to some degree. There is a need in the art for hearing assistance systems to provide diagnostic or calibration information to the physician, such as during the surgical implantation procedure, in order to ascertain efficacy and adjust therapy accordingly. There is a further need in the art for self-calibration of such hearing assistance systems to increase their ease of use.